Removal of trace organic chemicals in wastewater effluent by UV/H2O2 and UV/PDS

Maolida Nihemaiti; David B Miklos; Uwe Hübner; Karl G Linden; Jörg E Drewes; Jean-Philippe Croué

doi:10.1016/j.watres.2018.08.052

Removal of trace organic chemicals in wastewater effluent by UV/H₂O₂ and UV/PDS

Water Res. 2018 Nov 15:145:487-497. doi: 10.1016/j.watres.2018.08.052. Epub 2018 Aug 27.

Authors

Maolida Nihemaiti¹, David B Miklos², Uwe Hübner², Karl G Linden³, Jörg E Drewes², Jean-Philippe Croué⁴

Affiliations

¹ Curtin Water Quality Research Centre, Department of Chemistry, Curtin University, Perth, Australia.
² Chair of Urban Water Systems Engineering, Technical University of Munich, Munich, Germany.
³ Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, USA.
⁴ Curtin Water Quality Research Centre, Department of Chemistry, Curtin University, Perth, Australia. Electronic address: jean-philippe.croue@curtin.edu.au.

PMID: 30193192
DOI: 10.1016/j.watres.2018.08.052

Abstract

In this study, we comparatively investigated the degradation of 12 trace organic chemicals (TOrCs) during UV/H₂O₂ and UV/peroxydisulfate (PDS) processes. Second-order rate constants for the reactions of iopromide, phenytoin, caffeine, benzotriazole, and primidone with sulfate radical (SO₄^•-) were determined for the first time. Experiments were conducted in buffered pure water and wastewater effluent with spiked TOrCs. UV/PDS degraded all TOrCs more efficiently than UV/H₂O₂ in buffered pure water due to the higher yield of SO₄^•- than that of hydroxyl radical (^•OH) at the same initial molar dose of PDS and H₂O₂, respectively. UV/PDS showed higher selectivity toward TOrCs removal than UV/H₂O₂ in wastewater effluent. Compounds with electron-rich moieties, such as diclofenac, venlafaxine, and metoprolol, were eliminated faster in UV/PDS whereas UV/H₂O₂ was more efficient in degrading compounds with lower reactivity to SO₄^•-. The fluence-based rate constants ( [Formula: see text] ) of TOrCs in wastewater effluent linearly increased as a function of initial H₂O₂ dose during UV/H₂O₂, possibly due to the constant scavenging impact of the wastewater matrix on ^•OH. However, exponential increase of k_obs-UV/PDS with increasing PDS dose was observed for most compounds during UV/PDS, suggesting the decreasing scavenging effect of the water matrix (electron-rich site of effluent organic matter (EfOM)) after initial depletion of SO₄^•- at low PDS dose. Fulvic and humic-like fluorophores appeared to be more persistent during UV/H₂O₂ compared to aromatic protein and soluble microbial product-like fluorophores. In contrast, UV/PDS efficiently degraded all identified fluorophores and showed less selectivity toward the fluorescent EfOM components. Removal pattern of TOrCs during pilot-scale UV/PDS was consistent with lab-scale experiments, however, overall removal rates were lower due to the presence of higher concentration of EfOM and nitrite.

Keywords: Hydroxyl radical; Kinetics; Sulfate radical; Trace organic chemicals; UV-based advanced oxidation process; Wastewater treatment.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Hydrogen Peroxide
Organic Chemicals
Oxidation-Reduction
Ultraviolet Rays
Wastewater
Water Pollutants, Chemical*
Water Purification*

Substances

Organic Chemicals
Waste Water
Water Pollutants, Chemical
Hydrogen Peroxide